Associations between chronic stress, mental illness and poor oral health outcomes are well documented. These complex associations represent a bidirectional interplay among biological, behavioural, psychological and social processes. Furthermore, shared social determinants likely drive both mental health and oral health problems. This chapter reviews essential definitions, concepts and background related to the experience of chronic stress and mental disorders, preparing oral healthcare providers to work in increasingly multidisciplinary, comprehensive and person-centred care settings. It also examines literature demonstrating links between mental health and oral health, alongside conceptual and clinical considerations. Finally, this chapter emphasises the importance of training in integrated oral and behavioural healthcare to ensure optimal care for dental patients experiencing chronic stress or mental health issues.